Method and system for color correction of image signals

ABSTRACT

In a method and system for performing color correction for an image signal, a first set of matrix coefficients for color correction of the image signal in a 3-dimensional RGB color space is transformed to a first set of points of a two-dimensional XY plane. In addition, the first set of points is modified to a second set of points in the XY plane for tuning image quality. Furthermore, the first and second sets of points in the two-dimensional XY plane are displayed such as on a graphical user interface of a computer system.

This application claims priority under 35 USC §119 to Korean PatentApplication No. 2006-17242, filed on Feb. 22, 2006 in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to color correction of an imagesignal, and more particularly, to tuning color correction matrixcoefficients with a visualization aid from transformation into an XYplane.

2. Background of the Invention

Equation 1 below shows a 3×3 color correction matrix used for colorcorrection of an image signal comprised of color signals Rin, Gin, andBin:

$\begin{matrix}{\begin{pmatrix}{Rout} \\{Gout} \\{Bout}\end{pmatrix} = {\begin{pmatrix}{r\; 1} & {g\; 1} & {b\; 1} \\{r\; 2} & {g\; 2} & {b\; 2} \\{r\; 3} & {g\; 3} & {b\; 3}\end{pmatrix}\begin{pmatrix}{Rin} \\{Gin} \\{Bin}\end{pmatrix}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

As shown, RGB (red, green, and blue) values of color signals Rin, Gin,and Bin are tuned to Rout, Gout, and Bout with the 3×3 matrix. That is,the tuned image signal has RGB values of Rout, Gout and Bout as shown inEquations 2, 3, and 4 below:Rout=r1*Rin+g1*Gin+b1*Bin  Equation 2Gout=r2*Rin+g2*Gin+b2*Bin  Equation 3Bout=r3*Rin+g3*Gin+b3*Bin  Equation 4

According to such mathematical models, matrix coefficients for a desiredcolor correction such as r1, g1, b1, r2, g2, b2, r3, g3, and b3, may beobtained. Herein, influence of gamma and shading are considered for thecolor correction coefficients for desired color correction. However,intuitive estimation of the color correction coefficients of the matrixfor the target color correction is difficult using the mathematicalmodels.

In the prior art, such color correction coefficients are not intuitivelyrecognized. Instead in the prior art, the image signals are tuned byrepeatedly modifying the color correction coefficients based on personalexperience without any regulated rules. Therefore, tuning the imagesignal according to the prior art is time consuming and requires mucheffort.

SUMMARY OF THE INVENTION

For a method and system for performing color correction for an imagesignal according to an aspect of the present invention, a first set ofmatrix coefficients for the image signal in a n-dimensional color spaceare transformed to a first set of points of a two-dimensional XY plane,with n being greater than 2. In addition, the first set of points ismodified to a second set of points in the XY plane for tuning imagequality. Furthermore, the first and second sets of points in thetwo-dimensional XY plane are displayed such as on a graphical userinterface of a computer system.

In another embodiment of the present invention, the second set of pointsin the XY plane is transformed to a second set of matrix coefficients inthe n-dimensional color space.

In a further embodiment of the present invention, the first matrixcoefficients and the second matrix coefficients are each for arespective 3×3 matrix of color correction values in RGB color space.

In another aspect of the present invention, a respective coefficient sumof each of all rows of the matrix coefficients is equal to a same valuesuch as 1 for example.

In another embodiment of the present invention, the first set of pointsare modified to the second set of points by changing distance of each ofthe first to third point of the first set to the origin of the XY plane.

In a further embodiment of the present invention, the origin of the XYplane is a center point of a unit cube of the RGB color space. Inaddition, a Y axis of the XY plane is a line connecting the origin to aB axis of the RGB color space, and an X axis of the XY plane is a lineperpendicularly crossing the Y axis at the origin.

According to an example embodiment of the present invention, the firstset of matrix coefficients are transformed to the first set of points ofthe XY plane according to the following equations:xi=(gi−ri)/√{square root over (2)};andyi=(bi−di/3)*√{square root over (gi/2)};with xi and yi being a point in the XY plane for ri, gi, and birepresenting an i-th row for the first set of matrix coefficients in theRGB color space, and with di being a sum of ri, gi, and bi. In addition,the second set of points in the XY plane is transformed to the secondset of matrix coefficients in the RGB color space according to thefollowing equations:ri′=(−1/√{square root over (2)})*xi′−(1/√{square root over(6)})*yi′+di′/3;g1′=(1/√{square root over (2)})*x1′−(1/√{square root over(6)})*y1′+d1′/3;andb1′=(−2/√{square root over (6)})*y1′+d1′/3;with ri′, gi′, and bi′ representing an i-th row for the second set ofmatrix coefficients in the RGB color space, and with xi′ and yi′ beingmodified from xi and yi, and with di′ being a sum of ri′, gi′, and bi′.

In a further embodiment of the present invention, a first point of thefirst set is for a R among RGB, and is placed at a region between 150°and 270° from a positive X-axis of the XY plane. Additionally, a secondpoint of the first set is for a G among RGB, and is placed at a regionbetween 270° and 30° from the positive X-axis. Also, a third point ofthe first set is for a B among RGB, and is placed at a region between30° and 150° from the positive X-axis.

The present invention may be used to particular advantage when a memorydevice stores sequences of instructions (i.e., software) thereon.Execution of such sequences of instructions by a data processor causesthe data processor to perform the above stated steps for tuning such RGBcolor correction coefficients.

In this manner, the color correction coefficients of the RGB space aretransformed into the XY plane and are displayed for tuning withintuitive visualization.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent when described in detailed exemplaryembodiments thereof with reference to the attached drawings in which:

FIG. 1 is a flowchart of steps for performing color correction withvisualization according to an embodiment of the present invention;

FIG. 2 illustrates a two-dimensional XY plane transformed from athree-dimensional RGB space, according to an embodiment of the presentinvention;

FIG. 3 is a conceptual view illustrating transforming matrixcoefficients of the three-dimensional RGB space to points in thetwo-dimensional XY plane, in the steps of the flowchart of FIG. 1according to an embodiment of the present invention;

FIG. 4 illustrates three regions having the points of FIG. 3 in thetwo-dimensional XY plane, according to an embodiment of the presentinvention;

FIG. 5 is a block diagram of a system for performing the steps of theflowchart of FIG. 1, according to an embodiment of the presentinvention;

FIGS. 6A and 6B show an example display on a graphic user interface ofFIG. 5, according to an embodiment of the present invention; and

FIG. 7 is a conceptual view illustrating transforming points in the twodimensional XY plane back to matrix coefficients of thethree-dimensional RGB space, in the steps of the flowchart of FIG. 1according to an embodiment of the present invention.

The figures referred to herein are drawn for clarity of illustration andare not necessarily drawn to scale. Elements having the same referencenumber in FIGS. 1, 2, 3, 4, 5, 6A, 6B, and 7 refer to elements havingsimilar structure and/or function.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a flowchart of steps for performing color correction withvisualization according to an embodiment of the present invention. FIG.5 shows a block diagram of a system 500 for performing color correctionwith visualization according to an embodiment of the present invention.

Referring to FIG. 5, the system 500 includes a display device 530, adata processor 520, and a memory device 510 having sequences ofinstructions (i.e., software) stored thereon. Execution of suchsequences of instructions by the data processor 520 causes the dataprocessor 520 to perform the steps of the flowchart of FIG. 1. Thesystem 500 is a computer system in one example embodiment of the presentinvention. In that case, the display device 530 is a graphical userinterface screen.

Referring to FIGS. 1 and 5, the data processor 520 starts with a firstset of matrix coefficients such as r1, g1, b1, r2, g2, b2, r3, g3, andb3 for an initial 3×3 color correction matrix as represented byEquations 1, 2, 3, and 4 for example. Such matrix coefficients are for athree-dimensional RGB space. The data processor 520 transforms such afirst set of matrix coefficients r1, g1, b1, r2, g2, b2, r3, g3, and b3to a first set of points of a two-dimensional XY plane (step S10 of FIG.1).

In addition, according to an embodiment of the present invention, arespective sum of the ri, gi, and bi (with i=1, 2, and 3) matrixcoefficients is a same constant value such as 1. A respective sum di ofthe ri, gi, and bi (with i=1, 2, and 3) matrix coefficients for each rowof the initial 3×3 color correction matrix is represented by thefollowing Equations 5, 6, and 7:r1+g1+b1=d1  Equation 5r2+g2+b2=d2  Equation 6r3+g3+b3=d3  Equation 7In one example embodiment of the present invention, d1=d2=d3=1.

FIG. 2 illustrates determination of the two-dimensional XY plane fromthe three-dimensional RGB space, according to one example embodiment ofthe present invention. First, a unit cube is defined from points (1, 0,0), (0, 1, 0), and (0, 0, 1) in the three-dimensional RGB space. Acenter point that is equidistant from such points (1, 0, 0), (0, 1, 0),and (0, 0, 1) in the three-dimensional RGB space is determined to be anorigin (0, 0) of the two-dimensional XY plane.

In addition, a line connecting the origin (0, 0) to a B axis of the RGBspace is used as a Y axis of the XY plane, and an X axis of the XY planeis a line perpendicularly crossing the Y axis of the XY plane at theorigin (0, 0).

FIG. 3 is a conceptual view illustrating transformation of the first setof matrix coefficients of the three-dimensional RGB space to points inthe two-dimensional XY plane (step S110 of FIG. 1), according to anembodiment of the present invention. Referring to FIG. 3, a first point(r1, g1, and b1) in the three-dimensional RGB space is transformed intoa first point (x1, y1) in the two-dimensional XY plane.

Similarly, a second point (r2, g2, and b2) in the three-dimensional RGBspace is transformed into a second point (x2, y2) in the two-dimensionalXY plane. Furthermore, a third point (r3, g3, and b3) in thethree-dimensional RGB space is transformed into a third point (x3, y3)in the two-dimensional XY plane.

The points (x1, y1), (x2, y2), and (x3, y3) form a first set of pointsin the XY plane transformed from the first matrix coefficients (r1, g1,b1), (r2, g2, b2), and (r3, g3, b3), respectively, according to thefollowing Equations 8, 9, 10, 11, 12, and 13:x1=(g1−r1)/√{square root over (2)}  Equation 8y1=(b1−d1/3)*√{square root over (g1/2)}  Equation 9x2=(g2−r2)/√{square root over (2)}  Equation 10y2=(b2−d2/3)*√{square root over (g2/2)}  Equation 11x3=(g3−r3)/√{square root over (2)}  Equation 12y3=(b3−d3/3)*√{square root over (g3/2)}  Equation 13Generally, a point (xi, yi) of the first set of points in the XY planeis transformed from an i-th row of the first matrix coefficients (ri,gi, bi) according to the following Equations 14 and 15:xi=(gi−ri)/√{square root over (2)}  Equation 14yi=(bi−di/3)*√{square root over (gi/2)}  Equation 15

Further referring to FIGS. 1 and 5, the first set of points (x1, y1),(x2, y2), and (x3, y3) in the XY plane are displayed on the GUI screen530 (step S120 of FIG. 1). FIG. 6A is an example of such a GUI screendisplay 530 of the first set of points (x1, y1), (x2, y2), and (x3, y3)in the XY plane. FIG. 6A shows an example for when the first matrixcoefficients (r1, g1, b1), (r2, g2, b2), and (r3, g3, b3) in the RGBspace is (1, 0, 0), (0, 1, 0), and (0, 0, 1), respectively.

In addition, as illustrated in FIG. 4, each of the points (x1, y1), (x2,y2), and (x3, y3) in the XY plane is placed into a respective one ofthree regions in the XY plane. For example, the first point (x1, y1)derived from (r1, g1, b1) for the Rout signal is placed in a firstregion of the XY plane between 150° and 270° from a positive X-axis ofthe XY plane. The second point (x2, y2) derived from (r2, g2, b2) forthe Gout signal is placed in a second region of the XY plane between270° and 30° from the positive X-axis of the XY plane. The third point(x3, y3) derived from (r3, g3, b3) for the Bout signal is placed in athird region of the XY plane between 30° and 150° from the positiveX-axis of the XY plane.

Further referring to FIGS. 1 and 5, the data processor 520 tunes forimage quality by modifying the first set of points (x1, y1), (x2, y2),and (x3, y3) in the XY plane into a second set of points (x1′, y1′),(x2′, y2′), and (x3′, y3′) in the XY plane (step S130 of FIG. 1). In oneembodiment of the present invention, the first set of points (x1, y1),(x2, y2), and (x3, y3) in the XY plane are modified to the second set ofpoints (x1′, y1′), (x2′, y2′), and (x3′, y3′) by changing a position ofat least one point among the points of the first set (x1, y1), (x2, y2),and (x3, y3).

In one embodiment of the present invention, the second set of points(x1′, y1′), (x2′, y2′), and (x3′, y3′) of the XY plane are transformedback to the RGB space to the second set of matrix coefficients (r1′,g1′, b1′), (r2′, g2′, b2′), and (r3′, g3′, b3′) according to thefollowings.

First, a respective sum di of the ri, gi, and bi (with i=1, 2, and 3)matrix coefficients for each row of the second set of matrixcoefficients (r1′, g1′, b1′), (r2′, g2′, b2′), and (r3′, g3′, b3′) isrepresented by the following Equations 16, 17, and 18:r1′+g1′+b1′=d1′  Equation 16r2′+g2′+b2′=d2′  Equation 17r3′+g3′+b3′=d3′  Equation 18In one example embodiment of the present invention, d1′=d2′=d3′=1.

The second set of matrix coefficients (r1′, g1′, b1′), (r2′, g2′, b2′),and (r3′, g3′, b3′) is represented by the following equations 19, 20,21, 22, 23, 24, 25, 26, and 27:r1′=(−1/√{square root over (2)})*x1′−(1/√{square root over(6)})*y1′+d1′/3  Equation 19g1′=(1/√{square root over (2)})*x1′−(1/√{square root over(6)})*y1′+d1′/3  Equation 20b1′=(−2/√{square root over (6)})*y1′+d1′/3  Equation 21r2′=(−1/√{square root over (2)})*x2′−(1/√{square root over(6)})*y2′+d2′/3  Equation 22g2′=(1/√{square root over (2)})*x2′−(1/√{square root over(6)})*y2′+d2′/3  Equation 23b2′=(−2/√{square root over (6)})*y2′+d2′/3  Equation 24r3′=(−1/√{square root over (2)})*x3′−(1/√{square root over(6)})*y3′+d3′/3  Equation 25g3′=(1/√{square root over (2)})*x3′−(1/√{square root over(6)})*y3′+d3′/3  Equation 26b3′=(−2/√{square root over (6)})*y3′+d3′/3  Equation 27Generally, an i-th row of the second matrix coefficients (ri′, gi′, bi′)is transformed from a point (xi′, yi′) by the data processor 520 (stepS140 of FIG. 1) according to the following Equations 28, 29, and 30:ri′=(−1/√{square root over (2)})*xi′−(1/√{square root over(6)})*yi′+di′/3  Equation 28gi′=(1/√{square root over (2)})*xi′−(1/√{square root over(6)})*yi′+di′/3  Equation 29bi′=(−2/√{square root over (6)})*yi′+di′/3  Equation 30

FIG. 7 is a conceptual view illustrating transforming the second set ofpoints in the two-dimensional XY plane to the second set of matrixcoefficients of the three-dimensional RGB space (step S140 of FIG. 1),according to an embodiment of the present invention. Referring to FIG.7, the first modified point (x1′, y1′) in the two-dimensional XY planeis transformed to the first tuned point (r1′, g1′, and b1′) in thethree-dimensional RGB space.

Similarly, the second modified point (x2′, y2′) in the two-dimensionalXY plane is transformed to the second tuned point (r2′, g2′, and b2′) inthe three-dimensional RGB space. Furthermore, the third modified point(x3′, y3′) in the two-dimensional XY plane is transformed to the thirdtuned point (r3′, g3′, and b3′) in the three-dimensional RGB space.

Further referring to FIGS. 1 and 5, such a set of modified points (x1′,y1′), (x2′, y2′), and (x3′, y3′) in the XY plane is displayed on the GUIscreen 530 (step S150 of FIG. 1). FIG. 6B is an example of such a GUIscreen display 530 of the second set of points (x1′, y1′), (x2′, y2′),and (x3′, y3′) in the XY plane. The change of the position of the pointsof the second set (x1′, y1′), (x2′, y2′), and (x3′, y3′) in FIG. 6B fromthe position of the points of the first set (x1, y1), (x2, y2), and (x3,y3) in FIG. 6A provides a visualization of the color correction of theRin, Gin, and Bin of the image signals using the second set of matrixcoefficients (r1′, g1′, b1′), (r2′, g2′, b2′), and (r3′, g3′, b3′) ofthe RGB space. For example, the change of a third point of the secondset (x3′, y3′) from a third point of the first set (x3, y3) is largerthan the change for points (x1′, y1′) and (x2′, y2′) of the second set.The above changes visualize that the color correction of the Bincomponent is increased more than that of the Rin and Gin components.

In addition, FIG. 6B shows the example GUI screen 530 outputting thesecond set of matrix coefficients (r1′, g1′, b1′), (r2′, g2′, b2′), and(r3′, g3′, b3′) of the RGB space (step S160 of FIG. 1) corresponding tothe second set of points (x1′, y1′), (x2′, y2′), and (x3′, y3′) on theGUI screen. For example, FIG. 6B illustrates that (r1, g1, b1)=(1, 0, 0)has been tuned to (r1′, g1′, b1′)=(1.521, −0.434, −0.087). Similarly,FIG. 6B illustrates that (r2, g2, b2)=(0, 1, 0) has been tuned to (r2′,g2′, b2′)=(−0.423, 1.580, −0.157). Furthermore, FIG. 6B illustrates that(r3, g3, b3)=(0, 0, 1) has been tuned to (r3′, g3′, b3′)=(−0.249,−0.839, 2.088).

In one embodiment of the present invention, for improving sharpness ofthe image, the second set of points (x1′, y1′), (x2′, y2′), and (x3′,y3′) are vertexes of a triangle with an extended area from a triangledefined by points (x1, y1), (x2, y2), and (x3, y3) as its vertexes.

In this manner, the extent of tuning for image quality may be visualizedon the GUI screen to provide a user an intuitive sense of the extent oftuning for image quality. While the present invention has beenparticularly shown and described with reference to exemplary embodimentsthereof, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present invention as definedby the following claims.

The present invention is limited only as defined in the following claimsand equivalents thereof.

1. A method of performing color correction for an image signal,comprising: transforming a first set of matrix coefficients for colorcorrection of the image signal in a 3-dimensional RGB color space to afirst set of points of a two-dimensional XY plane display device;modifying the first set of points to a second set of points in the XYplane for tuning image quality, wherein said second set of points in theXY plane corresponds to a second set of matrix coefficients in said3-dimensional RGB color space with said second set of matrixcoefficients used for said color correction of the image signal withsaid tuned image quality; and displaying the first and second sets ofpoints in the two-dimensional XY plane.
 2. The method of claim 1,wherein the first and second sets of points in the two-dimensional XYplane are displayed on a GUI (graphical user interface) screen of acomputer system.
 3. The method of claim 1, further comprising:transforming the second set of points in the XY plane to said second setof matrix coefficients in the RGB color space.
 4. The method of claim 3,wherein a respective coefficient sum of each of all rows of the matrixcoefficients is equal to a same value.
 5. The method of claim 4, whereinthe same value is
 1. 6. The method of claim 5, wherein an origin of theXY plane is a center point of a unit cube of the RGB color space.
 7. Themethod of claim 6, wherein a Y axis of the XY plane is a line connectingthe origin to a B axis of the RGB color space, and an X axis of the XYplane is a line perpendicularly crossing the Y axis at the origin. 8.The method of claim 7, wherein the first set of matrix coefficients aretransformed to the first set of points of the XY plane according to thefollowing equations:xi=(gi−ri)/√{square root over (2)};andyi=(bi−di/3)*√{square root over (gi/2)}; with xi and yi being a point inthe XY plane for ri, gi, and bi representing an i-th row for the firstset of matrix coefficients in the RGB color space, and with di being asum of ri, gi, and bi; and wherein the method further includes the stepof: transforming the second set of points in the XY plane to a secondset of matrix coefficients in the RGB color space according to thefollowing equations:ri′=(−1/√{square root over (2)})*xi′−(1/√{square root over(6)})*yi′+di′/3;g1′=(1/√{square root over (2)})*x1′−(1/√{square root over(6)})*y1′+d1′/3;andb1′=(−2/√{square root over (6)})*y1′+d1′/3; with ri′, gi′, and bi′representing an i-th row for the second set of matrix coefficients inthe RGB color space, and with xi′ and yi′ being modified from xi and yiin said step B, and with di′ being a sum of ri′, gi′, and bi′.
 9. Themethod of claim 8, wherein a first point of the first set is for a Ramong RGB, and is placed at a region between 150° and 270° from apositive X-axis of the XY plane, and wherein a second point of the firstset is for a G among RGB, and is placed at a region between 270° and 30°from the positive X-axis, and wherein a third point of the first set isfor a B among RGB, and is placed at a region between 30° and 150° fromthe positive X-axis.
 10. The method of claim 9, wherein the first set ofpoints are modified to the second set of points by changing a positionof at least one point among the first through the third points of thefirst set.
 11. A system for performing color correction of an imagesignal, comprising: a display; a data processor; and a memory devicehaving sequences of instructions stored thereon, wherein execution ofthe sequences of instructions by the data processor causes the dataprocessor to perform the steps of: transforming a first set of matrixcoefficients for color correction of the image signal in a 3-dimensionalRGB color space to a first set of points of a two-dimensional XY plane;modifying the first set of points to a second set of points in the XYplane for tuning image quality, wherein said second set of points in theXY plane corresponds to a second set of matrix coefficients in said3-dimensional RGB color space with said second set of matrixcoefficients used for said color correction of the image signal withsaid tuned image quality; and displaying the first and second sets ofpoints and the two-dimensional XY plane on the display.
 12. The systemof claim 11, wherein the display is a GUI (graphical user interface)screen of a computer system.
 13. The system of claim 11, whereinexecution of the sequences of instructions by the data processor causesthe data processor to further perform the step of: transforming thesecond set of points in the XY plane to said second set of matrixcoefficients in the RGB color space.
 14. The system of claim 13, whereina respective coefficient sum of each of all rows of the matrixcoefficients is equal to a same value.
 15. The system of claim 11,wherein an origin of the XY plane is determined by the data processor asa center point of a unit cube in the RGB color space.
 16. The system ofclaim 15, wherein a Y axis of the XY plane is determined by the dataprocessor as a line connecting the origin to a B axis of the RGB colorspace, and an X axis of the XY plane is determined by the data processoras a line perpendicularly crossing the Y axis at the origin.
 17. Thesystem of claim 16, wherein the first set of matrix coefficients aretransformed by the data processor to the first set of points of the XYplane according to the following equations:xi=(gi−ri)/√{square root over (2)};andyi=(bi−di/3)*√{square root over (gi/2)}; with xi and yi being a point inthe XY plane for ri, gi, and bi representing an i-th row for the firstset of matrix coefficients in the RGB color space, and with di being asum of ri, gi, and bi; and wherein execution of the sequences ofinstructions by the data processor causes the data processor to furtherperform the step of: transforming the second set of points in the XYplane back to a second set of matrix coefficients in the RGB color spaceaccording to the following equations:ri′=(−1/√{square root over (2)})*xi′−(1/√{square root over(6)})*yi′+di′/3;g1′=(1/√{square root over (2)})*x1′−(1/√{square root over(6)})*y1′+d1′/3;andb1′=(−2/√{square root over (6)})*y1′+d1′/3; with ri′, gi′, and bi′representing an i-th row for the second set of matrix coefficients inthe RGB color space, and with xi′ and yi′ being modified from xi and yiin said step B, and with di′ being a sum of ri′, gi′, and bi′.
 18. Thesystem of claim 17, wherein a first point of the first set is for a Ramong RGB, and is placed by the data processor at a region between 150°and 270° from a positive X-axis of the XY plane, and wherein a secondpoint of the first set is for a G among RGB, and is placed by the dataprocessor at a region between 270° and 30° from the positive X-axis, andwherein a third point of the first set is for a B among RGB, and isplaced by the data processor at a region between 30° and 150° from thepositive X-axis.
 19. The system of claim 18, wherein execution of thesequences of instructions by the data processor cause the data processorto further perform the step of: modifying the first set of points to thesecond set of points by changing a position of at least one point amongthe first through the third points of the first set.
 20. A method ofperforming color correction for an image signal, comprising:transforming a first set of matrix coefficients for color correction ofthe image signal in a 3-dimensional RGB color space to a first set ofpoints of a two-dimensional XY plane; modifying the first set of pointsto a second set of points in the XY plane for tuning image quality; anddisplaying the first and second sets of points in the two-dimensional XYplane, wherein a respective coefficient sum of each of all rows of thematrix coefficients is equal to a same value.